The present invention relates to a communication system for controlling terminal units through boundary scan elements, and particularly to a communication system capable of coping with breakage of communication lines.
A boundary scan test method has been proposed as one of the inspection methods, with a plurality of IC chips arranged over a printed wire board with printed wiring formed thereon, to see whether or not connection between each IC chip and each printed wiring is properly made and whether or not each printed wiring is broken.
This boundary scan test method can be applied to integrated circuits (IC chips) into which boundary scan elements are incorporated. The boundary scan element, for example as shown in FIG. 4, includes a plurality of boundary cells 214 individually provided between input/output terminals of an internal logic circuit 211 for implementing the inherent functions of the integrated circuit 210 and input terminals 212 and output terminals 213 of the integrated circuit 210, a TAP controller (TAP circuits) 219 for controlling input and output of data to or from the boundary cells 214, a TDI terminal 220 for receiving test data, a TDO terminal for transmitting test data, a TCK terminal 222 into which a clock signal is input, and a TMS terminal 223 for receiving a mode signal for switching the operation mode of the TAP controller 219, and, if required, is further provided with a bypass register 215, an ID CODE register 216, an instruction register 217, a TRS terminal 224 for receiving a reset signal, or the like. The bypass register 215 is to transfer communication data without being passed through the boundary cells, the ID CODE register 216 outputs an individually-assigned ID CODE to identify the source of the communication data, and the instruction register 217 decodes specific data among the communication data to carry out the transition or the like of the operation mode independent of a TMS signal. In this connection, the bypass register 215 to instruction register 217 are referred to as boundary scan register (218).
To describe the respective terminals or the signals to be input/output through the respective terminals in detail, TDI (Test Data In) is a signal for serial-inputting instructions and data to a test logic, and is sampled at rising edges of TCK. TDO (Test Data Out) is a signal for serial-outputting data from the test logic, the output value being changed at falling edges of TCK. TCK (Test Clock) supplies a clock to the test logic. It is a dedicated input for enabling the use of a serial test data path independent of the system clock inherent to the component. TMS (Test Mode Select) is a signal for controlling the test operation, and is sampled at rising edges of TCK. The TAP controller decodes this signal. TRST (Test Reset) is a negative logic symbol for asynchronously initializing the TAP controller, and is optional.
The integrated circuit 210 into which such boundary scan element is incorporated can run a test on the operating state thereof and the connecting relationship between this integrated circuit 210 and external devices, by the procedures described below.
First, in checking the quality of the internal logic 211 of the integrated circuit 210, serial data (test data) are input to the TDI terminal 220 of the integrated circuit 210 as they are shifted, and thereby the test data are set into respective boundary cells 214 corresponding to respective input terminals 212. In this state, the integrated circuit 210 is operated before the data set in the respective boundary cells 214 corresponding to respective output terminals 213 are shifted for output from the TDO terminal 221, and, on the basis of the corresponding relationship between the serial data (test result data) thus obtained and the test data input to this integrated circuit 210, the internal logic 211 of the integrated circuit 210 is tested for its quality.
The boundary scan test method can also be carried out on a plurality of integrated circuits as long as the boundary scan elements are incorporated therein.
For example, a plurality of integrated circuits 210 mounted on a substrate 226 as shown in FIG. 5 can also be subjected to a test for breakage and the like of the printed patterns between the integrated circuits 210, along with a test on the integrated circuits 210 themselves.
In this case, the respective boundary scan elements incorporated in the plurality of integrated circuits 210 are connected in series with-each other. Specifically, the TDO terminal 221 of the first integrated circuit 210 (the left in the drawing) and the TDI terminal 220 of the second integrated circuit 210 (the right in the drawing) are connected with each other, the output terminal 229 of a boundary scan controller board 228 provided in host computer unit 227 or the like and the TDI terminal 220 of the first integrated circuit 210 are connected with each other, and the input terminal 230 of the boundary scan controller board 228 and the TDO terminal 221 of the second integrated circuit 210 are connected with each other. The test procedures are as follows:
In testing breakage, short circuit, and the like of the printed patterns, a test data preparing tool 231 or the like is used to prepare test data (serial data), which is output from the output terminal 229 of the boundary scan controller board 228 and is input to the TDI terminal 220 of the first integrated circuit 210 while shifted, setting the test data into the respective boundary cells 214 corresponding to the respective output terminals 213 in this integrated circuit 210. In this state, the data stored in these respective boundary cells 214 are output from the respective output terminals 213 provided in the first integrated circuit 210 as shown in FIG. 6, and are input through the respective printed patterns 233 constituting a system bus and the like to the respective input terminals 212 of the second integrated circuit 210, and further captured into the respective boundary cells 214 corresponding to these respective input terminals 212.
Thereafter, the data stored in the respective boundary cells 214 of these respective integrated circuits 210 are shifted and captured through the input terminal 230 of the boundary scan controller board 228 as they are analyzed by using a test result analyzing tool 232 or the like, so that a test can be made for breakage, short circuit, and the like in such a test range 235 as the printed patterns 233 providing connection between the integrated circuits 210.
Next, in inspecting the internal logic 211 of the respective integrated circuits 210, test data are output from the output terminal 229 of the boundary scan controller board 228, and are input to the TDI terminal 220 of the first integrated circuit 210 as they are shifted, so as to be set into the respective boundary cells 214 corresponding to the respective input terminals 212 of this integrated circuit 210 as shown in FIG. 6.
Subsequently, this integrated circuit 210 is operated, and the resulting data are captured into the respective boundary cells 214 corresponding to the respective output terminals 213 before the data stored in these respective boundary cells 214 are shifted for output from the TDO terminal 221 of the first integrated circuit 210. Here, the second integrated circuit 210 is brought into a bypass state as shown in FIG. 7 by the boundary scan controller board 228, so that the data output from the TDO terminal 221 are bypassed through the second integrated circuit 210 and captured through the input terminal 230 of the boundary scan controller board 228. Then, the test analyzing tools 232 or the like can be used for analysis of the captured data to test whether or not the first integrated circuit 210 operates properly.
Next, in the cases of inspecting the second integrated circuit 210, the boundary scan controller board 228 similarly brings the first integrated circuit 210 into a bypass state as shown in FIG. 7 before test data are output from the output terminal 229 of the boundary scan controller board 228 and bypassed through the first integrated circuit 210. Then, the test data are input to the TDI terminal 220 of the second integrated circuit 210 while shifted, to be set into the respective boundary cells 214 corresponding to the respective input terminals 212 of this integrated circuit 210 as shown in FIG. 8. Subsequently, this integrated circuit 210 is operated, and the resulting data are captured into the respective boundary cells 214 corresponding to the respective output terminals 213. Thereafter, the data stored in the respective boundary cells 214 are shifted for output from the TDO terminal 221, and further they are captured through the input terminal 230 of the boundary scan controller board 228. Then, the captured data can be analyzed by using the test result analyzing tool 232 and the like, so as to test whether or not the second integrated circuit 210 operates properly.
In this way, a substrate 226, as long as using integrated circuits 210 into which boundary scan elements are incorporated, can be tested for the quality of the respective integrated circuits 210 themselves, and on the connecting relationship between the integrated circuits 210 and the like by implementing the boundary scan test, method.
Now, it was found by the present inventor that when integrated circuits into which such boundary scan elements are incorporated are used to constitute the substrate or the like of a sensor module, input and output of serial data can be made to or from the respective integrated circuits mounted on the substrate 226 at a speed on the order of 20 Mbps without the use of communication integrated circuits or the like.
Then, a communication system was proposed which applies the boundary scan elements to carry out communication with host computer units and the like without the use of communication devices.
FIG. 9 is a block diagram showing an example of the communication system to which the boundary scan elements are applied.
The communication system 240 shown in this figure comprises: a communication controller unit 241 for carrying out the transmitting, collection, and the like of communication data; a plurality of sensor units 242a-242c for carrying out the monitoring of an object to be monitored; a plurality of boundary scan elements 243a-243c provided for each of these sensor units 242a-242c, the boundary scan elements carrying out such processing as capturing the control data output from the aforesaid communication controller unit 241 to supply the same to the respective sensor units 242a-242c, and capturing the detected data output from the respective sensor units 242a-242c to supply the same to the aforesaid communication controller unit 241; and communication lines 244 for providing connection between the respective boundary scan elements 243a-243c and the aforesaid communication controller unit 241.
The respective boundary scan elements 243a-243c are connected in series to the communication controller unit 241. Specifically, the connection is made in such a manner that the output terminal 241a of the communication controller unit 241 is connected to the TDI terminal of the boundary scan element 243a, and the TDO terminal of the boundary scan element 243a is connected to the TDI terminal of the next boundary scan element 243b, the TDO terminal of the boundary scan element 243b is connected to the TDI terminal of the boundary scan element 243c, and the TDO terminal of the boundary scan element 243c is connected to the input terminal 241b of the communication controller unit 241.
The function of this communication system 240 is as follows:
The respective boundary scan elements 243a-243c function in synchronization with the clock signal transmitted from the TCK. terminal 241d of the communication controller unit 241, and the operation mode of the respective TAP controllers is switched by the TMS signal transmitted from the TMS terminal 241c of the communication controller unit 241.
In driving the respective sensor units 242a-242c according to the instruction from the host computer unit 245, control data (serial data) are output from the output terminal 241a of the communication controller unit 241, and the data are supplied to the respective boundary scan elements 243a-243c and set into the boundary cells corresponding to the output terminals. Then, the control data set are output from the output terminals, and supplied to the respective sensor units 242a-242c corresponding to the respective boundary scan elements 243a-243c, thereby driving the units.
Moreover, in the cases of collecting the detected data or the like from the respective sensor units 242a-242c according to the instruction from the host computer unit 245, the detected data or the like of the respective sensor units 242a-242c are once set in the boundary cells associated with the input terminals of the corresponding, respective boundary scan elements 243a-243c. Then, the data are output as serial data from the TDO terminals, and captured through the input terminal 241b of the communication controller unit 241.
Such communication system 240, when setting control data into the respective boundary scan elements 243a-243c and when outputting the detected data and the like from the respective boundary scan elements 243a-243c, can be maximized to 20 Mbps in data rate, thereby allowing the transfer of communication data at higher speeds than those of conventional communication systems.
In the communication system 240, however, when the communication line 244 is broken at any point, e.g. between the boundary scan element 243b and the boundary scan element 243c, it becomes impossible for the communication controller unit 241 to obtain communication data from any of the boundary scan elements 243a-243c; besides, it is also difficult to pinpoint the breakage.
It is an object of the present invention to provide a communication system which uses boundary scan elements capable of coping with the breakage of communication lines.
According to the present invention, there is provided a communication system comprising: a boundary scan element including a plurality of boundary cells individually assigned to respective input terminals and output terminals, a TAP circuit for controlling input and output of data to or from the aforesaid boundary cells, a TDI terminal for inputting serial data to be supplied to the aforesaid boundary cells, a TDO terminal for outputting data from the aforesaid boundary cells as serial data, a TCK terminal to which a clock signal is input, and a TMS terminal to which a mode signal for switching the operation mode of the aforesaid TAP circuit is input; a plurality of terminal units connected with each of the aforesaid boundary scan elements or provided with an IC into which the elements are incorporated; a communication controller, connected in series with the aforesaid boundary scan elements, for transmitting/receiving through the aforesaid boundary scan elements communication data for individually controlling the aforesaid terminal units; and a cable provided to establish connection between the aforesaid boundary scan elements adjoining each other and between the aforesaid boundary scan elements and the aforesaid communication controller, the aforesaid cable being formed by binding up a clock signal line, a mode signal line, an outgoing communication line, and incoming communication lines, wherein the aforesaid incoming communication lines establish individual connection between a data input terminal of the aforesaid communication controller and the aforesaid TDO terminal of the aforesaid boundary scan element directly connected with the aforesaid communication controller through the aforesaid cable, and between the aforesaid TDO terminal and the aforesaid TDI terminal of the aforesaid boundary scan elements adjoining each other, and that the aforesaid outgoing communication line establishes connection between a data output terminal of the aforesaid communication controller and the aforesaid TDI terminal of the aforesaid boundary scan element positioned at the backmost as seen from the aforesaid communication controller.
In this invention, communication data are transferred in the direction from the boundary scan element which is positioned at the backmost as seen from the communication controller to the boundary scan element which is directly connected with the communication controller. Accordingly, even in the cases where breakage of communication lines occurs between the boundary scan elements, the communication data held in the boundary scan element or elements positioned on the communication controller side from the breakage can be transferred to the communication controller, so that the communication controller can identify the presence/absence of breakage and the approximate position of the breakage by the communication data transferred.
Moreover, according to the present invention, there is provided a communication system comprising: a plurality of boundary scan elements including a plurality of boundary cells individually assigned to respective input terminals and output terminals, a TAP circuit for controlling input and output of data to or from the aforesaid boundary cells, a TDI terminal for inputting serial data to be supplied to the aforesaid boundary cells, a TDO terminal for outputting data from the aforesaid boundary cells as serial data, a TCK terminal to which a clock signal is input, and a TMS terminal to which a mode signal for switching the operation mode of the aforesaid TAP circuit is input; a plurality of terminal units (gag connected with the aforesaid boundary scan elements or provided with an IC into which the elements are incorporated; and a communication controller for transmitting/receiving through the aforesaid boundary scan elements communication data for individually controlling the aforesaid terminal units, wherein the aforesaid terminal units each is connected with a boundary scan element group or provided with an IC into which the elements are incorporated, that the aforesaid boundary scan element group including two boundary scan elements having the aforesaid input terminals and the aforesaid output terminals separately connected in parallel, the aforesaid communication controller includes two terminal areas comprising a communication data output terminal for transmitting communication data to the aforesaid boundary scan elements and a communication data input terminal for receiving communication data from the aforesaid boundary scan elements, and that either one of the aforesaid terminal areas and the other of the aforesaid terminal areas are connected in series with either ones one of the aforesaid boundary scan elements in the aforesaid boundary scan element groups and the others of the aforesaid boundary scan elements in the aforesaid boundary scan element groups, respectively, so that the directions of transfer of communication data are opposite to each other.
In this invention, two of the boundary scan elements are assigned to the respective terminal units, and the respective boundary scan elements are connected with the communication controller so that the directions of transfer of communication data are opposite to each other. Therefore, only either one of the boundary scan elements is normally used for communication processing, and when the communication lines suffer breakage, the others of the boundary scan elements are used for communication processing, thereby allowing input and output of communication data to or from all of the terminal units.
In the communication systems of the present invention, the terminal units include various sensor units, such as monitoring camera units. And, in the connection between the terminal units and the boundary scan elements, the output terminals and the input terminals are connected with input terminals of the terminal units and output terminals of the terminal units, respectively, and thereby the data of the boundary cells are output to the terminal units and data are conversely input to the boundary cells.
The communication data include not only the control data to be transmitted to the terminal units in order to control the terminal units, but also data detected by the terminal units to be transmitted from the terminal units and status data such as whether or not the terminal units are driven normally.